Public Safety Alliance- Dedicated to First Responders… First

Frequently Asked Questions

Why does public safety need the D block spectrum?

Public Safety has identified a host of applications for broadband; failure to reallocate the D block will limit public safety’s ability to get full use of those applications and to ensure effective interoperability across all levels of government. Failure to reallocate the D block also continues the same past history of providing public safety too little spectrum, which results in the need for future allocations that ultimately have to be sourced from another spectrum band, further hampering interoperability.

Why can’t roaming onto carrier networks eliminate the need to dedicate the D block to public safety?

Public safety has first hand knowledge of the need to control its communications networks. Many disaster situations have shown that commercial systems get clogged with drastic increase in demand. Even priority (without pre-emption) access on a clogged commercial system does not guarantee public safety access to the capacity it will need. Furthermore, commercial systems are necessarily built to meet the needs of consumers, not the higher levels of reliability, availability, in-building coverage, and user feature flexibility inherent in dedicated public safety networks.

What is the impact to the public of removing the D block from the auction?

First, dedicating spectrum to further empower Public Safety with broadband tools benefits the entire public community being served by police officers, firefighters and emergency medical personnel. Without adequate safety and homeland security, the entire U.S. economy and way of life suffers.

Second, removing the 10 MHz of the D block from the auction would be only a 2% impact on the 500 MHz the FCC has targeted for overall commercial broadband operations. In contrast, auctioning the D block will cut the spectrum needed for public safety broadband in half.

The FCC has suggested that it will give Public Safety additional spectrum sometime later, why isn’t that good enough?

The fact that the D Block is right next to the Public Safety band allows Public Safety to build one network, double its capacity, solve the interference issue, and allow Public Safety to keep up with advancing tools. Having the two bands combined to serve one network significantly reduces the cost and complexity of the network equipment and devices compared to having the spectrum split across two non-adjacent bands. Additionally, by combining the two bands, Public Safety could utilize the entire 10 MHz where having the D Block separated will necessitate wasting spectrum to carve out a guard band between D Block and Public Safety.

What profile of users would utilize the Public Safety broadband network?

The Public Safety broadband network will provide enhanced communications capabilities for state and local police, fire & emergency medical services, first and foremost. Public Safety operations require multi-agency coordination. Even a medium-level incident may call in over 100 responders and over 50 vehicles – all requiring coordinated, interoperable communications. The 2007 Minneapolis I-35 bridge collapse had over 128 agencies involved in the rescue operations.

In addition, there are several other potential groups of users for the network that would bring great benefit. First, interoperability during an incident is enhanced if access is given to those maintaining critical infrastructure (in the event of a sewer pipe or water main rupture, HazMat contamination of the water supply, damage to electrical equipment, etc.) as well as various federal agencies. Second, there is great benefit to the ever-present need to reduce cost without degrading performance by moving services off of other subscription networks (e.g. move call boxes off leased wired lines, move traffic light control off leased wired lines, enable parking meters to transmit status, move back-up telephony off commercial networks). By example, New York DoITT has moved several such services onto their data network. And keep in mind that the non-mission critical services can be de-prioritized during an incident should there be a bandwidth constraint. Third, new machine-to-machine applications offer great promise for early detection and identification of dangers across a wide area (e.g. chemical sensors of the water supply and infrastructure, vibration sensors of bridges and other structures, gunshot sensors in urban areas and movement sensors at borders).

What kinds of applications will be served on a Public Safety broadband network?

Public safety agencies will be able to both utilize the data applications in place today with faster, more responsive performance increasing their utility as well as offer access to a whole array of advanced, multimedia applications that take advantage of key enablers including:

  • Bi-directional, vehicular video
  • Location aware real-time services
  • Mobile office, in-field productivity
  • Multimedia command & control
  • Dynamic mapping, weather & traffic flows
  • Content-rich lookups to complex databases

The Public Safety broadband network will provide greater efficiencies in day-to-day public safety operations, management of emergency incidents and major events, as well as providing the critical support needed for catastrophic incidents.

How do we know what quality of video is really required for Public Safety operations?

The Department of Homeland Security has established the working group Video Quality in Public Safety (VQiPS) to determine standards around video presentation in various Public Safety use cases. While the industry awaits the analysis and outcomes from the working group, Public Safety agencies along with leading technology vendors have conducted extensive investigations into video quality tiering and alignment to Public Safety needs. For example, New York’s DoITT (Department of Information Technology and Telecommunications) has demonstrated requirements for 1-2 Mbps cameras (D1) supporting fixed and mobile operations and LAPD has demonstrated requirements for 3 Mbps fixed camera video streams.

Won’t increasing advancements in video technology allow us to transmit higher quality video using less spectrum in the near future?

On the one hand, video encoding and compression advancements anticipated in the next decade will increase the optimization of rate control, motion estimation, and adaptive noise reductions, and thereby shrink the transmit size of a given video stream. And we will see some improvements in the LTE technology over time. But consider also that the number of users on both the Public Safety and the commercial networks will continue to grow. In addition, as history on both Public Safety and commercial networks will show, valuable new applications will come to market that need more and more bandwidth. Public Safety and the FCC all anticipate that Public Safety will need more bandwidth to accommodate this trend. Today, we know that 10 MHz alone will not support Public Safety video applications offering the lowest acceptable quality for real-time incident scene decision-making. Thorough analysis and modeling by Public Safety agencies and leading vendors have considered the state-of-the-art, best-in-class techniques for video encoding and compression to determine the baseline capacity needs from the broadband network. Public Safety’s bandwidth constraints will only worsen with time.

Why can’t Public Safety use delayed video or image grabs to alleviate the capacity concerns?

Delayed video is video that is transmitted at a lower rate (bits per second) than the rate at which it was captured (seemingly because of a limitation in the network’s transmission capacity or in an attempt to take advantage of non-real-time compression techniques). Transmitting video in this way causes two problems. First, the video showing on the other end will not be real-time. Second, since the outgoing bits move more slowly than the incoming bits, the camera’s buffer will fill and it will have to stop recording until it catches up. Video transmission that is not real-time and has large holes endangers the response by influencing decisions based on mis-information regarding the current state of the situation. Image grabs (i.e. transmitted pictures) present the same problem, but are even more limiting. For example, assessing whether an incident is escalating (decision: send more resources) or calming down (decision: do not send any more resources or switch to clean-up resources) would be severely impaired. Decisions made and actions taken can determine the extent of lost lives and damage. The most effective Public Safety response will require real-time, situational awareness of the incident as it unfolds.

Why can’t Public Safety use their 4.9 GHz band to support broadband services?

The higher frequency range of a 4.9 GHz network translates to shorter propagation of the signal. Therefore while it is not well-suited for a wide-area implementation; it works best for local area “hot spots” such as the 5 GHz “hot spot” networks in many Starbucks. Characteristically, any given area would have decidedly less than 50% coverage by a “hot spot.” Using a 4.9 GHz “hot spot” for an incident presents three problems. First, a 4.9 GHz network would have to be deployed at the scene for the large majority of incidents. The initial minutes of a public safety emergency response are critical and precious time would be lost. Second, 4.9 GHz is not only characterized by short propagation, but also poor in-building penetration. Consider a HazMat incident where a well-protected First Responder suited with sensors, a video camera, etc. enters a highly contaminated building (e.g. a clandestine lab). He must be able to communicate with commanders and various experts that are outside the building. Third, an agency’s Emergency Operations Center and other non-field commanders are most often located off-site (e.g. at the police station). A 4.9 GHz “hot spot” will not transmit over those long distances.

How will auctioning the D Block to a commercial operator result in coverage holes for Public Safety?

The FCC plan takes away the one guarantee Public Safety holds most precious - a communications lifeline to their supervisors, peers, dispatch. Interference based coverage holes will result in unexpected & unpredictable dropped calls for emergency responders.

  • Coverage holes appear due to adjacent channel interference between D Block Base Sites and Public Safety Base Sites
  • The coverage holes may appear anywhere across the broadband coverage area as RF shadowing and multipath phenomenon create unpredictable coverage gaps where a user connection would become suddenly terminated
  • The probability of a coverage hole appearing increases when the Public Safety user travels toward the coverage edge of a Public Safety Base Site and arrives in proximity to a D Block site
  • As the D Block commercial operator builds out their network to increase coverage in “hot spots” or indoor locations using microcells or picocells; the probability of a coverage gap will increase
  • Users travelling within 80 meters of a D Block site increase their probability of a suddenly terminated session by over 20% and a capacity degradation of over 50%

Couldn’t filters be used to suppress the interference between the D Block and the Public Safety PSST spectrum?

Even with advanced interference mitigation techniques between the D Block & Public Safety networks, coverage gaps cannot be avoided and Public Safety may have their communications terminated. Advanced RF techniques including filters, forced guard band, power trimming, and spectral shaping cannot resolve the severity of this interference.

If priority & pre-emption are so critical to Public Safety and absent in commercial LTE technology, why aren’t leading LTE vendors building this capability into the commercial platforms?

It is imperative that Public Safety technology be built on standards-based platforms to ensure interoperability and maximum benefits from scale economies. The 3GPP standards body that is driving the LTE standard serves the very large commercial cellular market, led by the most successful cellular operators. The financial opportunity that the Public Safety market represents is quite small compared to the larger commercial market. Any features that are unique to Public Safety, such as priority and pre-emption, just can’t compete with the commercial features, and there is much LTE standard to be written around identified commercial features.

Why can’t commercial carriers provide Public Safety with prioritized broadband capacity needed during critical incidents?

Commercial LTE systems do not have the ability to dynamically engage prioritization to Public Safety. As a result during a critical incident, Public Safety responders may not be able to access the LTE system immediately and have to compete for access with commercial users.

Additionally, commercial LTE prioritization policy cannot distinguish between Public Safety incidents. There is no ability to distinguish between a cat in a tree or a 4 alarm fire. Commercial LTE prioritizes services based on the device; Public safety LTE networks prioritize based on the individual & the nature of the situation – the device may be of least importance.

A Public Safety responder handing over to the commercial network looking for capacity may discover that the sites are down or overloaded and drop service. There is no LTE device visibility to the status of other networks and no guarantee that capacity will be available when switching between networks.

Large scale incidents requiring public safety to utilize commercial spectrum, are the times history has proven commercial networks to be the least available

What is “pre-emption” and why is this important to Public Safety?

“Pre-emption” is the ability to force non-priority users off of the network during emergency incidents to direct necessary capacity to critical resources. This is an important feature that is built into the foundation of Public Safety mission critical voice communication systems.

Why can’t Public Safety rely on commercial carriers to provide pre-emption capabilities during critical incidents?

Pre-emption is not supported by commercial networks. Once a user is already on a commercial LTE system, there is no mechanism to kick them off or even stop from occupying more capacity. This is a trick that the press has come to learn very well, using it to their advantage during incidents by never releasing their cell phone connections.

How will the FCC plan compromise multi-agency interoperability?

The FCC plan takes a giant step backwards in enabling multi-agency interoperability during critical incidents. Public Safety responders operating on multiple cellular carriers will not be capable of participating in common talk groups; this could result in chaos at an incident scene. To enable this interoperability requires technical capabilities and operating agreements that have never existed between cellular operators, and that operators have little incentive to implement. Eventually a centralized provisioning authority may need to be created to govern and administer Public Safety roaming at public expense, and charges to roaming Public Safety responders can be expected to be significant.

How does the FCC plan eliminate competition and fair play among commercial carriers?

The FCC Plan eliminates competition and hampers fair play, to the disadvantage of both Public Safety & commercial carriers. There is only one option (as challenged as it is in other ways) to manage the interference between the Public Safety block and the D block: the Public Safety and D Block site deployments must be collocated and coordinated. Public Safety will have no option but to work exclusively with the D Block winner.

Public Safety agencies will be disadvantaged because their freedom of choice is removed and the D Block winner becomes a sole-source partner for life. Public Safety will be forced to the terms and conditions of a sole-source vendor motivated by consumer services. Maintenance and service upgrades of shared equipment will be dictated by the priorities of a profit-motivated consumer-focused business who knows they have a captive audience.

Commercial carriers are disadvantaged by being kept from effectively competing on a level playing field to win new Public Safety LTE business. Additionally, all existing Public Safety subscriptions are likely to churn to the D Block winner

How is the interference issue associated with the D Block and Public Safety spectrum similar to the 800 MHz Re-Banding effort?

In July of 2004, the FCC adopted a plan to reconfigure the 800 MHz band to address the growing problem of harmful interference to 800 MHz public safety communication systems caused by high-density commercial wireless systems. The plan called for Sprint Nextel to swap spectrum with several public safety licensees in the 800 MHz to curb the harmful interference to public safety systems. The project plan was estimated at 36 months with an estimated cost of $850M with a required $2.5B guarantee for provisional funds - 5 years and $4B later the plan is still in progress.

Sign Up For Updates

© 2010 Public Safety Alliance. All Rights Reserved.